System for acquiring seismic data in a marine environment, using seismic streamers coupled to means for detecting and/or locating marine mammals

ABSTRACT

Discloses herein is a system of acquiring seismic date in a marine environment, which includes: seismic streamers towed by a vessel; and means for detecting and/or locating marine mammals, characterized in that said marine mammal detection and/or location means are secured to said seismic streamers.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. patent applicationSer. No. 12/415,087 filed on Mar. 31, 2009 which claims the benefit ofFrench Patent Application No. FR 08/01814 filed on Apr. 2, 2008, theseapplications are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention is that of the acquisition of seismic data.More precisely, the invention relates to equipment for analyzing the seabed. The invention relates in particular to the oil prospecting industryusing the seismic method, but can apply to any field using a system foracquiring seismic data in a marine environment.

2. Background of the Invention

The operations of acquiring geophysical data on site conventionally usenetworks of sensors (designated by the term “hydrophones” with regard tothe acquisition of data in a marine environment). The hydrophonesmentioned previously are distributed along cables in order to formlinear acoustic antennae normally referred to as “streamers” or “seismicstreamers”. The network of seismic streamers is towed by a seismic boat.A seismic streamer consists of an assembly of individual sectionsinstrumented with seismic sensors and associated analogue to digitalconversion electronics. The seismic boat also tows one or more seismicsources consisting of a network of air cannons, water cannons oracoustic vibrators. The pressure wave generated by the seismic sourcepasses through the column of water and insonifies the upper layers ofthe sea bed. Part of the signal is refracted by the interfaces andinhomogeneities of the ocean crust.

The resulting acoustic signals are then detected by the seismic sensorsdistributed over the entire length of the seismic streamers. Theseacoustic signals are processed, digitized and retransmitted by thetelemetry from the seismic streamers to the operator station situated onthe seismic boat, where the processing of the raw data is carried out.

To have a correct image of the mapping of the sea bed in the explorationzone, it is important to precisely locate the seismic sensorsdistributed along the seismic streamers as well as the seismic source.This location of the streamers is important, in particular in order to:

-   -   follow the position of the hydrophones in order to obtain        satisfactory precision in the image of the sea depths;    -   detect the movements of the streamers in relation to each other;    -   follow the navigation of the streamers, in particular in a        situation of passing round an obstacle such as an oil barge.

It should be noted that seismic streamers consist of an assembly ofsections generally having a length of approximately 150 metres, thestreamers being able to have a total length of several kilometres (6 to7 kilometres, but possibly ranging up to 10 or even 12 kilometres).

Various methods are used for precisely locating the position of theseismic sensors distributed along the streamers. Initially, thepositioning of the marine seismic streamers and seismic source have beenbased on the use of GPS receivers, distributed at a few particularpoints (boat, buoys supporting seismic source, buoys at the head andtail of the streamers, etc), and magnetic compasses distributed inlarger numbers along the streamers (these compasses making it possibleto determine deformations in the streamers). Currently the techniquesfor positioning marine seismic streamers are more efficient. They stilluse GPS positioning in order to have the absolute geographical referenceframe, but they associate with this the use of submarine acoustics inorder to determine the distances between acoustic modules mounted alongthe seismic streamers. These acoustic modules may be transmitters and/orreceivers and make it possible to determine the distances between theadjoining modules situated on the various streamers. There are thenavailable, in order to achieve precise positioning of all the streamers,reference points given by the GPS receivers and a mesh of inter-moduleand therefore inter-streamer distances.

SUMMARY OF THE INVENTION

The disclosure herein provides a system for acquiring seismic data in amarine environment, which includes:

-   -   seismic streamers towed by a vessel;    -   means for detecting and/or locating marine mammals,        characterised in that the marine mammal detection and/or        location means are secured to the seismic streamers.

In one embodiment, the streamers each include means for transmittingdata to a master controller on board the vessel and in that the marinemammal detection and/or location means are intended to communicate withthe data transmission means integrated in the seismic streamers in orderto transmit data to the master controller.

In another embodiment, the system includes means for detecting positionsof the streamers and data transmission means integrated in the seismicstreamers intended to transmit the positions to the master controller.

In another embodiment, the marine mammal detection and/or location meansare associated with means for processing data issuing from the marinemammal detection and/or location means, the processing means beingsecured to the streamers.

In another embodiment, the marine mammal detection and/or location meansare integrated in self-contained modules clamped to the seismicstreamers.

In another embodiment, the seismic streamers include at least one coilallowing inductive coupling of the modules with the data transmissionmeans integrated in the seismic streamers.

In another embodiment, the seismic streamers each include a plurality ofsections, the marine mammal detection and/or location means beinginterposed between two of the sections.

In another embodiment, the marine mammal detection and/or location meansinclude self-contained electrical supply means.

In another embodiment, the seismic streamers include electrical supplymeans, the marine mammal detection and/or location means being suppliedby the seismic streamer electrical supply means.

In another embodiment, the marine mammal detection and/or location meansare integrated in modules that include a section including firstacoustic reception means dedicated to a marine mammal detection and/orlocation function and second acoustic reception means dedicated to afunction of positioning the streamers in relation to each other, thefirst and second acoustic reception means being distinct.

In another embodiment, the marine mammal detection and/or location meansare integrated in modules that include a section including acousticreception means common to a marine mammal detection and/or locationfunction and to a function of positioning the seismic streamers inrelation to each other.

In another embodiment, the marine mammal detection and/or location meansare associated with means for emitting acoustic signals deterring marinemammals.

In another embodiment, the marine mammal detection and/or location meansare integrated in modules that include a section including firstacoustic emission means dedicated to a function of deterring marinemammals and second acoustic emission means dedicated to a function ofpositioning the seismic streamers in relation to each other, the firstand second acoustic emission means being distinct.

In another embodiment, the marine mammal detection and/or location meansare integrated in modules that include a section including acousticemission means common to a function of deterring marine mammals and afunction of positioning the seismic streamers in relation to each other.

In another embodiment, the system includes navigation control meanscoupled to the streamers in order to act at least on the immersedposition of the streamers, the navigation control means being integratedin modules that include the navigation control means.

Another aspect of the invention described herein provides a method ofacquiring seismic data in a marine environment implementing a systemwherein a master controller on board the vessel dynamically configureseach acoustic module constituting the network in order to ensure eitherthe acoustic positioning of the seismic streamers or the detection ofmarine mammals or an acoustic repellent function.

DESCRIPTION OF THE FIGURES

Other characteristics and advantages of the invention will emerge moreclearly from a reading of the following description of severalembodiments of the invention, given by way of illustrative andnon-limitative example, and the accompanying drawings, among which:

FIG. 1 is a schematic representation of a first embodiment of theinvention according to which the marine mammal detection and/or locationmodules are clamped to the seismic streamers;

FIGS. 2 and 3 are each a schematic representation of a variant of thefirst embodiment illustrated by FIG. 1;

FIG. 4 is a schematic representation of a second embodiment of theinvention according to which the marine mammal detection and/or locationmeans are integrated in the length of the seismic streamers;

FIGS. 5 to 8 are each a schematic representation of a variant of thesecond embodiment illustrated by FIG. 4;

FIGS. 9 to 11 are each a schematic representation of a variant of thesecond embodiment illustrated by FIG. 4, including navigation controlmeans integrated in the marine mammal detection and/or location modules.

DETAILED DESCRIPTION

One problem relating to oil prospecting by 3D marine seismic survey isthe monitoring of marine mammals during the exploration campaign.International regulations in this regard and the recommendations ofcompetent bodies encourage marine seismic operators to carry out, inparallel to their measurement campaign, continuous monitoring fordetecting the possible presence of marine mammals in the explorationzone for purposes of protection.

This monitoring is carried out either visually by one or more humanoperators or using an independent system of acoustic receiver orreceivers fulfilling functions of passive detection, classification andgeographical location of the marine mammal or mammals. These acousticsystems, commonly referred to as “PAM” (passive acoustic monitoring),are intended for this use. They consist of acoustic receivers, ingeneral one or more streamers dedicated to this function, associatedwith a remote processing unit, for example on the seismic vessel. Theyare self-contained and can or should be deployed in parallel to theseismic streamers.

The equipment often associated with the passive monitoring of marinemammals is the “acoustic deterring” of marine mammals. This equipmentemits artificial acoustic signals in order to drive away mammals beforethe implementation of activities assumed to be dangerous for thesespecies.

Currently, the positioning of the seismic streamers towed by the seismicboat on the one hand, and on the other hand the passive monitoring ofmarine mammals (PAM) as well as the function of acoustic deterring ofthe mammals, are independent functionalities.

In other words, the seismic boat tows in particular:

-   -   one or more seismic sources;    -   a network of seismic streamers, over the length of which the        seismic sensors are distributed;    -   transducers, the function of which is to participate in the        positioning of the seismic streamers, these transducers being        able to be integrated on the streamers;    -   acoustic modules, the function of which is to participate in the        monitoring of mammals;    -   and possibly acoustic repellents.

It will therefore be understood that the positioning of the seismicstreamers and the monitoring of marine mammals are functionally andstructurally independent.

The result of this is:

-   -   an increase in the complexity of all the means towed by the        seismic boat, giving rise to consequent work in terms of        logistics (storage, deployment, redeployment, management of        positions with a view to preventing collisions, etc);    -   an increase in complexity at the system level with the        management of various systems for positioning the seismic        streamers, monitoring marine mammals and deterring marine        mammals;    -   high costs because of the increase in the means used.

The objective of the invention is in particular to mitigate thesedrawbacks of the prior art.

More precisely, the objective of the invention is to propose a systemfor acquiring seismic data in a marine environment making it possible tomore effectively integrate in the towed network the functions and meansrelating to the monitoring of marine mammals.

Another objective of the invention is to provide such a system that alsomakes it possible to more effectively integrate the function ofdeterring (distancing) marine mammals.

Another objective of the invention is to provide such a system thatmakes it possible to optimize the size of the means deployed and towedby the seismic boat.

Another objective of the invention is to provide such a system thatmakes it possible to reduce the logistic resources relating inparticular to the storage and deployment/redeployment of the meanscontributing to the positioning of the seismic boat and the monitoringof marine mammals.

Yet another objective of the invention is to provide such a system thatmakes it possible to envisage a reduction in investment associated withthe means contributing to the positioning of the seismic streamers andthe monitoring of marine mammals.

An additional objective of the operation is to have a high-level systemmanagement that integrates the various functionalities (positioning ofseismic streamers; detection, classification and location of marinemammals; and deterring of marine mammals) in order to offer seismicoperators an integrated and ergonomic management system.

These objectives, as well as others that will emerge hereinafter, areachieved by virtue of the invention, the object of which is a system ofacquiring seismic data in a marine environment, comprising:

-   -   seismic streamers towed by a vessel;    -   means for detecting and/or locating marine mammals,

characterized in that said means for detecting and/or locating marinemammals are secured to said seismic streamers.

Thus, by virtue of the invention, the distribution, in the towednetwork, of the functions (and corresponding structural means) relatingto the monitoring of marine mammals is optimised.

This is because the invention affords optimization of the size of themeans deployed and towed by the seismic vessel.

According to one advantageous solution, said streamers each includemeans for transmitting data to a master controller on board said vessel,said means for detecting and/or locating marine mammals being intendedto communicate with said data transmission means integrated in saidseismic streamers in order to transmit data to said master controller.

Preferentially, the system comprises means for detecting positions ofsaid streamers and in that said data transmission means integrated insaid seismic streamers are intended to transmit said positions to saidmaster controller.

In this way, the means for transmitting integrated data to the seismicstreamers are, according to the invention, taken advantage of totransmit to the master controller the data supplied by:

-   -   the streamer position detection means;    -   the means for detecting and/or locating marine mammals.

The invention therefore provides a system having a level of integrationsuperior to that of prior systems, since the data transmission meansintegrated in the seismic streamers are common to the streamer positiondetection means and to the marine mammal detection and/or locationmeans.

It should be noted that the components for detecting and/or locatingmarine mammals may be the same (in this case the hydrophones) as thosethat provide the acquisition of seismic data.

In addition, such a solution makes it possible to envisage a reductionin investment, some components being common to the streamer positiondetection means and to the marine mammal detection and/or locationmeans, while they were duplicated in the systems of the prior art.

According to one advantageous solution, said marine mammal detectionand/or location means are associated with means for processing dataissuing from said marine mammal detection and/or location means, saidprocessing means being secured to said streamers.

In this way, the data supplied by said detection and/or location meansare processed locally, which avoids transmitting raw data to the mastercontroller on board the vessel and consequently avoids using some of theresources (processing and/or computing capacities) of the mastercontroller.

According to a first embodiment, said marine mammal detection and/orlocation means are integrated in self-contained modules clamped to saidseismic streamers.

The modules are then mechanically coupled to the seismic streamers, at apoint on the seismic streamer intended for this mechanical coupling.

In this case, said seismic streamers include at least one coil allowinginductive coupling of said modules with said data transmission meansintegrated in said seismic streamers.

In this way a wireless link is implemented between the module and thestreamers with regard to the transmission of PAM data intended for themaster controller.

According to a second embodiment, said seismic streamers each comprise aplurality of sections, said marine mammal detection and/or locationmeans being interposed between two of said sections.

In such a configuration, a relatively high level of integration isobtained since, in addition to the data transmission means common to thestreamer position detection means and the marine mammal detection and/orlocation means, the modules including the marine mammal detection and/orlocation means are included in the length of the seismic streamers andno longer independent of these.

Such a configuration therefore proves to be particularly advantageouswith regard to:

-   -   the optimization of the size of the means deployed and towed by        the seismic vessel;    -   the operation of the PAM system since there is no longer any        need to manage the periodic renewal of the module energy unit;    -   the logistic savings able to be obtained, with regard to the        storage, deployment/redeployment of all the means making up the        towed network, and the management of the positions of the        various components of this network.

This is because, with regard to the management of the positions of thevarious components of this network, the management of the positions ofthe seismic streamers takes place so as to be merged with that of thepositions of the modules including the marine mammal detection and/orlocation means.

According to a variant embodiment, said marine mammal detection and/orlocation means comprise self-contained electrical supply means.

According to another variant embodiment said seismic streamers includeelectrical supply means, said marine mammal detection and/or locationmeans being supplied by said electrical supplies of said streamers.

It will be understood that this second variant embodiment reduces theoperating costs of the system by eliminating the constraint of themanagement of self-contained energy systems (periodic battery changes).

According to a first approach of the invention, said marine mammaldetection and/or location means are integrated in modules comprising asection including first acoustic reception means dedicated to a marinemammal detection and/or location function and second acoustic receptionmeans dedicated to a function of positioning said streamers in relationto each other, said first and second acoustic reception means beingdistinct.

According to a second approach of the invention, said marine mammaldetection and/or location means are integrated in modules comprising asection including acoustic reception means common to a marine mammaldetection and/or location function and to a function or positioning saidseismic streamers in relation to each other.

It will be understood that this second approach helps to furtherincrease the level of integration of the marine mammal detection and/orlocation means and the means for positioning the seismic streamers inrelation to each other.

According to another characteristic of the invention, said marine mammaldetection and/or location means are associated with means for emittingacoustic signals deterring marine mammals.

In this case, according to a first embodiment, said marine mammaldetection and/or location means are integrated in modules comprising asection integrating first acoustic emission means dedicated to afunction of deterring marine mammals and second acoustic emission meansdedicated to a function of positioning said seismic streamers inrelation to each other, said first and second acoustic emission meansbeing distinct.

According to a second embodiment, said marine mammal detection and/orlocation means are integrated in modules comprising a section includingacoustic emission means dedicated to a function of deterring marinemammals and to a function of positioning said seismic streamers inrelation to each other.

Once again, this second embodiment helps to further increase the levelof integration of the various components.

According to an advantageous variant, the system comprises navigationcontrol means coupled to said streamers in order to act at least on theposition of said streamers with respect to immersion (depth), saidnavigation control means being integrated in modules comprising saidnavigation control means.

According to this configuration, the following are merged in the sameassembly:

-   -   the acoustic positioning functionalities of the seismic        streamers;    -   the marine mammal monitoring functionalities (PAM);    -   and optionally the dynamic streamer control functionalities (the        part usually referred to as the “Bird”).

The invention also concerns a method of acquiring seismic data in amarine environment using a system as described above, characterized inthat a master controller on board said vessel dynamically configureseach acoustic module constituting the network in order to provide eitherthe acoustic positioning of the seismic streamers, or the detection ofmarine mammals, or an acoustic deterring function.

As indicated previously, the principle of the invention lies inproposing a seismic data acquisition system in which data transmissionmeans integrated in the seismic streamers are common to the transmissionof data issuing from streamer position detection means and those issuingfrom marine mammal detection and/or location means, the latter beingintegrated in modules coupled to the seismic streamers.

FIG. 1 provides a schematic representation of a first embodiment of theinvention.

According to this embodiment, the modules 2 are clamped to the seismicstreamers 1 by means for clamps 3. Thus the modules 2 extend alongsidethe seismic streamers, substantially parallel to the correspondingportion of the streamers.

The clamping means are of the type currently used for clamping theacoustic positioning modules or the speed measurement modules or thecompass modules or the immersion measurement modules, modules known topersons skilled in the art.

According to the present embodiment, the modules 2 each comprise:

-   -   a body 201 that contains the energy, the electronics and the        inductive coupling system;    -   reception acoustics composed of a hydrophone moulded onto the        body 201.

FIG. 2 illustrates a variant embodiment of this first embodiment.According to this variant, the modules 2 each comprise:

-   -   a section 202 integrating the acoustic reception means 21 (in        this case a group of hydrophones);    -   a body 201 integrating means for processing and transmitting        acoustic signals supplied by the acoustic reception means 21.

Moreover, in a system such as the one illustrated by FIG. 1 or the oneillustrated by FIG. 2, it will be noted that:

-   -   the dialogue between the module 2 and the corresponding streamer        is effected by inductive coupling with a coil 12 integrated in        the seismic streamers. The transmission of the data is effected        by a twisted pair of so-called modem wires 10, conventionally        passing through the streamers and connecting the coils 12 in        order to transmit supplied data to the master controller;    -   self-contained electrical supply means 23 are integrated in the        module 2 and supply the energy necessary for the functioning of        the processing and transmission means integrated in the body        201, as well as to the acoustic reception means 21.

The originality of the configuration described by FIGS. 1 and 2 lies inusing the seismic streamers equipped with coils as a functional supportfor the PAM function. This affords several advantages:

-   -   great latitude of positioning of the PAM function;    -   great ease of implementation;    -   real-time dialogue through the “modem” pair of wires connecting        the inductive coupling coils of the seismic streamer.

FIG. 4 illustrates schematically a second embodiment of the invention.

According to this embodiment, the modules 2 are integrated in line withthe seismic streamers, along the length of these.

To do this, the seismic streamers being composed of a plurality ofsections 11, the modules 2 are interposed between two of these sections11.

In this case, the module 2 may be either self-contained in terms ofenergy, or supplied from an electrical supply line 110 integrated in theseismic streamers.

The dialogue between the module 2 and the streamer 1 is effected eitherby the “modem” pair of wires 10, or be another pair of wires runningthrough the streamer (such as for example the pair of telemetry wires).

A more integrated configuration consists of integrating in the samemodule the acoustic positioning functionalities of the seismic streamersand the marine mammal monitoring functionalities.

Such a configuration is shown schematically by FIG. 5.

According to this configuration, the module is integrated between twosections 11 of a seismic streamer 1. The module 2 consists of a metalbody 201 (or made from other material) and a mini-section 202integrating acoustic means 22, consisting of a transducer that,according to this configuration, may:

-   -   either fulfil the function of acoustic positioning of the        seismic streamers; in this case the acoustic transducer 22 is        used in transmission/reception mode;    -   or fulfil the function of acoustic receiver for the monitoring        of marine mammals; in this case, the acoustic transducer 22 is        used in reception mode only.

The dialogue between the module 2 and the corresponding seismic streamer1, as far as the master controller 30 on board the seismic boat 32, isimplemented by the pairs of telemetry wires integrated in the seismicstreamers.

The electrical supply to the modules 2 is effected from supply lines 110integrated in the seismic streamers 1.

Another variant of the second embodiment consists of integrating severaldistinct acoustic elements in the mini section 202 of the module 2,namely:

-   -   a transducer 22 intended for the positioning of the seismic        streamers;    -   a set of hydrophones 21 intended for the marine mammal        monitoring function.

This variant is illustrated by FIG. 6.

In the context of the invention, it is also possible to integrate in themodule 2 the function of “acoustic repellent”, in addition to thefunctions of acoustic positioning of the marine seismic streamers andpassive monitoring of marine mammals.

The module 2 then has a triple functionality:

-   -   the acoustic positioning of the marine seismic streamers by        means for the transducers 22;    -   passive monitoring of marine mammals using acoustic receivers        21;    -   the function of acoustic repellent of marine mammals, using        acoustic emitters 24.

It should be noted that the acoustic emission of the artificial signalsnecessary for the acoustic repellent function can be achieved either bythe transducer used for the acoustic positioning of the seismicstreamers or by a transducer dedicated to this function of acousticrepellent.

In the same way as for the previous configurations, such atriple-functionality module 2 could be either clamped to the seismicstreamer (FIG. 3) or interposed between two sections 11 of the seismicstreamer 1 (FIG. 7).

FIG. 8 shows an even more integrated configuration of the systemaccording to the invention, with a “triple function” module 2.

In this configuration, a single acoustic transducer 25 fulfils the threeacoustic functions, namely:

-   -   transmission/reception of the acoustic signals intended for the        positioning of the seismic streamers;    -   reception of the acoustic signals emitted by marine mammals;    -   emission of acoustic signals used as a repellent for marine        mammals.

The configuration depicted by FIG. 9 is a version of the systemaccording to the invention integrating navigation control means(conventionally referred to by the term “Bird”) intended to act on thedepth of the streamer and possibly on the lateral position of thestreamers.

In this case, the module 2 includes, in addition to the previousversions, the functionality of dynamic control of the seismic streamer.In this case it fulfils a triple functionality:

-   -   the acoustic positioning of the seismic streamers by means for        example of an acoustic transducer 22;    -   dynamic control (navigation) of the streamer;    -   passive acoustic monitoring of marine mammals.

Another variant of the system illustrated by FIG. 9 is shownschematically by FIG. 10. According to this variant, the mini-section202 of module 2 includes several acoustic elements, namely:

-   -   transducer 22 intended for the positioning of the seismic        streamers;    -   a set of hydrophones 21 intended for the PAM function;    -   and possibly a transducer intended for the acoustic repellent        function.

The modules of the systems illustrated by FIGS. 9 and 10, which providethe merging of the acoustic positioning and marine mammal monitoringfunctionalities with optionally dynamic control of the streamers andacoustic repellent are distributed along the marine seismic streamersand allow a more or less dense geographical meshing, according to thenumber of modules deployed, of the whole of the streamer network.

The supervision system situated on board the vessel can communicate,through the telemetry box of the seismic streamers, with all the modulesdeployed in the network of streamers.

The information concerning the propagation times for the acoustic pathsbetween the modules distributed along the streamers (the functionalityused for the positioning of the seismic streamers) as well as the dataof the PAM function and possibly the data for managing the birds andcontrolling the acoustic repellents go back to the supervision station,where the processing operations of the highest level will be performed.

With regard to the system aspect, the merging of the “hardware”functions of positioning the seismic streamers, marine mammal monitoringand possibly dynamic control of the streamers extends to the merging ofthe supervision software 34 for these functions. In other words, asingle supervision software package 34 provides the navigation(positioning and dynamic control) of the complete network of seismicstreamers and includes the functionalities intended for monitoringmarine mammals (detection, classification and location).

The originality of the configuration described above is therefore basedon several characteristics:

-   -   merging in the same module of the functions of positioning of        the seismic streamers, optionally integrating therein the        dynamic control of the streamers, and monitoring of marine        mammals;    -   merging of these same functionalities at the operator station,        which affords maximum integration of these requirements called        on to coexist and consequently optimum ergonomics for the        operators of the geophysical prospection;    -   great flexibility of deployment of the PAM function: the PAM        modules are implicitly distributed all along the seismic        streamers. In particular the supervision software 34 can use the        spatial diversity of the modules to allow optimization of the        processing operations adapted to the location of marine mammals        (PAM functionality).

With reference to FIG. 11, the function of “acoustic repellent” formarine mammals can also be associated with the previously mentionedfunctions.

The module will then have a triple or even quadruple functionality:

-   -   acoustic positioning of the marine seismic streamers;    -   passive monitoring of marine mammals;    -   the function of acoustic repellent of marine mammals;    -   and possibly the function of dynamic control of the seismic        streamers.

In this configuration, a single acoustic transducer 25 fulfils the threeacoustic functions (in a similar fashion to the system in FIG. 8described above).

In general terms, the acoustic emission of the artificial signalsnecessary for the acoustic repellent function can be achieved either bythe transducer used for the acoustic positioning of the seismicstreamers or by a transducer dedicated to this repellent function.Because of the size of the acoustics that can be integrated in theacoustic section, the acoustic repellent will be oriented at medium andhigh frequency (typically from 10 to 100 kHz) and will be ratherintended to drive away pinnipeds and odontocetes.

It should be noted that the seismic source or sources can also be usedas a low-frequency acoustic repellent (frequencies<10 kHz) for drivingaway large cetaceans. In this operating mode the emission power iscontrolled and the regulatory constraints concerning the mitigationmethods (rise in power over time) are complied with.

In the versions of the system illustrated by FIGS. 9 to 11, which mergeall the functionalities, the system software will supervise all thefunctions:

-   -   location and navigation of the seismic streamers;    -   passive monitoring of the marine mammals (detection,        classification and location);    -   medium- and low-frequency acoustic repellent;    -   low-frequency acoustic repellent;    -   mitigation process.

From an operating point of view, the system deployed will be organisedin different operating phases.

For example, a typical functioning could be:

-   -   after deployment of the network of streamers, and before the        activation of the seismic sources: monitoring of the operating        field in order to ensure that marine mammals are not present;    -   if marine mammals are present: implementation of the mitigation        procedures, with possibly the use of medium- and/or        high-frequency repellents (acoustic modules) and/or low        frequency repellents (seismic sources);    -   if no marine mammals are present: seismic operating phase, with        positioning of the streamers by the supervision software for the        spatio-temporal synchronisation of seismic data.

Throughout this seismic exploitation phase, the supervision system canassign modules in bioacoustic signal receiving mode (PAM detectionfunction integrated at the acoustic module level);

-   -   if a bioacoustic signal is detected by a module, the information        will be sent back to the supervisor, triggering the appropriate        procedure:    -   confirmation of detection of marine mammal;    -   location of the bioacoustic source;    -   if there is a mammal in the nuisance zone, stoppage of seismic        shootings;    -   monitoring of the movement of the mammal;    -   activation of the marine mammal classification procedures with        possible use of repellents.

The seismic activities are resumed when the area is clear.

What is claimed is:
 1. A seismic acquisition system comprising: astreamer; a seismic source; plural seismic sensors distributed along thestreamer and configured to record seismic data representative of asubsurface illuminated by acoustic waves generated by the seismicsource; passive mammal monitoring sensors distributed along the streamerand configured to record mammal related data associated with a marinemammal; a communication cable for transmitting the seismic data and themammal related data; and a control device connected to the communicationcable and configured to receive the seismic and mammal related data andto determine a presence of the marine mammal based on the mammal relateddata.
 2. The system of claim 1, wherein the seismic sensors and thepassive mammal monitoring sensors are integrated inside the streamer. 3.The system of claim 1, wherein the streamer is formed of plural sectionsconnected to each other, the plural sections include (i) at least apassive mammal monitoring section that includes the passive mammalmonitoring sensors and (ii) at least a seismic section that includes theseismic sensors.
 4. The system of claim 3, wherein the passive mammalmonitoring section is free of seismic sensors and the seismic section isfree of passive mammal monitoring sensors.
 5. The system of claim 1,wherein the control device is configured to locate the marine mammal. 6.The system of claim 5, wherein the control device is further configuredto monitor a movement of the marine mammal.
 7. The system of claim 6,wherein the control device is further configured to classify the marinemammal.
 8. The system of claim 5, wherein the control device is furtherconfigured to inform an operator about a presence of the marine mammal.9. The system of claim 8, wherein a seismic shooting is stopped to limitcontact with the marine mammal.
 10. The system of claim 1, wherein thecontrol device is configured to control an emission power of the sourcebased on regulatory constraints for the subsurface when a presence ofthe marine mammal is detected.
 11. The system of claim 1, wherein thecontrol device is configured to drive the source to provide a repellantfunction for the marine mammal.
 12. The system of claim 1, wherein thepassive mammal monitoring sensors are used for acoustic positioning ofother streamers.
 13. The system of claim 1, wherein the passive mammalmonitoring sensors are located inside corresponding modules that areused to provide dynamic control of the streamer.
 14. The system of claim1, wherein the passive mammal monitoring sensors are located insidecorresponding modules that are used for acoustic positioning of otherstreamers, to provide a repellant function for the marine mammal, and toprovide dynamic control of the streamer.
 15. The system of claim 1,further comprising: location sensors distributed along the streamer andconfigured to provide acoustic positioning data related to otherstreamers.
 16. The system of claim 15, further comprising: datatransmission means connected to the location sensors and the passivemammal monitoring sensors and configured to transmit both the mammalrelated data and the acoustic positioning data.
 17. The system of claim15, wherein the location sensors and the passive mammal monitoringsensors are located in a same section, between seismic sections thatinclude the seismic sensors.
 18. A seismic acquisition systemcomprising: a streamer; a seismic source; plural sensors distributedalong the streamer and configured to record seismic data representativeof a subsurface illuminated by acoustic waves generated by the seismicsource and also configured to record mammal related data associated witha marine mammal; a communication cable for transmitting the seismic dataand the mammal related data; and a control device connected to thecommunication cable and configured to receive the seismic and mammalrelated data and to determine a presence of the marine mammal based onthe mammal related data.
 19. A streamer system comprising: pluralseismic sensors distributed along a streamer and configured to recordseismic data representative of a subsurface illuminated by acousticwaves generated by a seismic source and also configured to record mammalrelated data associated with a marine mammal; a communication cableextending through the streamer and configured to transmit the seismicdata and the mammal related data; and a control device connected to thecommunication cable and configured to receive the seismic and mammalrelated data and to determine a presence of the marine mammal based onthe mammal related data.